Doesn’t it go into the back of the radio mate?
If you have a changer already and use it (I do still) you can get one that goes into the aux socket. Unless you’re using that as well?
Anyway I think you can find them on eBay relatively cheap.
I've read they plug into the CD changer port, in the boot behind the carpet. Apparently..
There are a few different versions, though, so some may plug directly into the rear of the Business head unit.
It is no unusual to ask here first - I had a spare one which I sold here when I got one as part of the Carphonics installation. The car already had a Grom unit, so didnt need another one. But it was a CD changer end plug in unit yes.